As wireless communication standards evolve, a need has arisen for a mobile terminal that accommodates both the Global System for Mobile Communication (GSM) standard and Wide-Band Code Division Multiple Access (WCDMA) standards, such as the Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access Frequency Division Duplex (UTRA/FDD) standard. A mobile terminal accommodating both of these standards includes transmit and receive circuitry for GSM operation and transmit and receive circuitry for UTRA/FDD operation. Since it is also desirable for the mobile terminal to include a single antenna, there remains a need for a switch architecture that couples transmit and receive circuitry for GSM operation to the antenna during GSM operation and couples transmit and receive circuitry for UTRA/FDD operation to the antenna during UTRA/FDD operation.
A conventional switch architecture that may be used for this purpose simply includes controllable switches for coupling each of the transmit and receive paths for GSM operation to the antenna during GSM operation and a controllable switch for coupling the UTRA/FDD transceiver to the antenna during UTRA/FDD operation. However, a major problem for this architecture is intermodulation distortion. More specifically, during UTRA/FDD operation, the transmit frequency from the UTRA/FDD transceiver mixes with blocking signals, such as transmit signals from nearby mobile terminals, to produce intermodulation distortion that disturbs the UTRA/FDD reception and degrades the operation of the mobile terminal.
Thus, there remains a need for a switch architecture that reduces or substantially eliminates non-linearities during FDD operation such that a magnitude of intermodulation distortion during FDD operation is substantially reduced.